Pd-Ag membranes for auto-thermal ethanol reforming

The auto-thermal ethanol reforming was carried out at 200 kPa by a two-step process consisting of a traditional reformer operating at high temperature (700-740 degrees C) and a Pd-Ag multitube membrane module where the separation of hydrogen took place at 350-380 degrees C. The membrane module was a bundle of I I thin-wall Pd-Ag tubes of wall thickness 50-60 mu m, diameter 10 mm, and length 270 mm: permeation tests were performed at 300-395 degrees C with lumen pressure of 150-200 kPa, and nitrogen sweep flow rates in the shell side ranged from 10 to 30 l min(-1) at atmospheric pressure. A hydrogen permeance Pe = 1.317 x 10(-2) exp (-3.622 x 10(3)/T(K)) mol m(-2) s(-1) Pa-0.5 was measured and complete hydrogen selectivity was verified. A water/ethanol Mixture of molar ratio 2.50/1.00 was used as feed stream for carrying Out ethanol reforming in the traditional fixed-bed reactor filled with a Ni on alumina catalyst. As a second step, the water gas shift (WGS) membrane reaction was carried out in the multitube membrane reactor: the Pd-Ag alloy of the membrane tubes worked for both catalyzing the reaction and for separating all the hydrogen produced in the reformer and in the membrane reactor itself. The hydrogen separated through the membrane was collected in the shell side of the membrane module: by operating with a water/ethanol feed flow rate of 200 g h(-1), up to 1.2 l min(-1) of pure hydrogen was produced. (C) 2009 Curtin University of Technology and John Wiley & Sons, Ltd.